1. Technical Field
The present invention relates to a liquid ejecting head and a liquid ejecting apparatus that each include a piezoelectric element including a piezoelectric layer made of a piezoelectric material and electrodes, and that eject droplets from nozzle apertures, and relates to the piezoelectric element.
2. Related Art
Ink jet recording heads are a typical type of liquid ejecting head. For example, an ink jet recording head includes a vibration plate defining a part of a pressure generating chamber communicating with nozzles through which ink droplets are discharged. In the ink jet recording head, a piezoelectric element deforms the vibration plate to apply a pressure to the ink in the pressure generating chamber, thereby discharging ink droplets through the nozzles. Some of the piezoelectric elements used in ink jet recording heads have a structure in which a piezoelectric layer made of a piezoelectric material capable of electromechanical conversion, such as a crystallized dielectric material, is disposed between two electrodes.
The piezoelectric material of the piezoelectric layer of such a piezoelectric element is required to have high piezoelectric properties. In order that the piezoelectric layer exhibits satisfactory piezoelectric properties, it is desirable that the piezoelectric material be oriented parallel to any of the {100} planes in a rhombohedral system. In order to orient lead zirconate titanate (PZT) in a direction parallel to a {100} plane, for example, seed titanium may be used in a piezoelectric layer (for example, JP-A-2011-238774 and JP-A-2005-340428). JP-A-2011-238774 discloses a method for manufacturing a piezoelectric element in which a lead titanate layer is used as a seed layer so that the piezoelectric layer can be oriented in a direction parallel to a {100} plane. Also, JP-A-2005-340428 discloses the technique of orienting the piezoelectric layer in a direction parallel to a {100} plane by using a buffer layer containing an elemental metal that can form the B site of PZT crystals as an orientation control layer.
However, if such an orientation control layer is used, the titanium in the orientation control layer is diffused upward or oxidized, consequently increasing the area of electrical conduction failure in the lower electrode is disadvantageously increased. Also, thermal reaction or the like between the titanium in the orientation control layer and the lead zirconate titanate of the piezoelectric layer reduces the crystallinity of the piezoelectric layer at the vicinity of the lower electrode, thereby degrading piezoelectric properties. Accordingly, an orientation control layer is desired which can suppress the diffusion of titanium and help the piezoelectric layer exhibit satisfactory piezoelectric properties.
This issue can arise not only in an actuator installed in a liquid ejecting head such as an ink jet recording head, but also in actuators in other apparatuses.